This invention relates to a process for improving an optical contact between a patternwise powdery coating layer and a substrate, and to a phosphor screen provided according to the present process.
The phosphor screen of a color picture tube has been so far prepared through steps of forming a mixture layer of phosphor powders and photosensitive resin on the inner surface of a face plate, a light exposure, development, and drying. Thus, the phosphor powders are bonded to the substrate while being covered with the photosensitive resin insolubilized by light exposure. The photosensitive resin is removed by panel baking, after a metal back layer made of aluminum vapor-deposited film has been formed on the back side of the phosphor layer. Consequently, a space having at least a depth corresponding to the thickness of the insolubilized photosensitive resin is formed between the phosphor powders and the glass surface of the face plate.
In the conventional phosphor layer structure, a portion R.sub.1 of fluorescence L generated within phosphor 1 by impingement of electron beams is reflected on the surface of phosphor 1, and the fluorescence L transmitted through the surface of phosphor 1 proceeds in vacuum, as shown in FIG. 1. Then, a portion R.sub.2 of the transmitted fluorescence L is reflected on the inner surface of face plate 2, and then a portion R.sub.3 of the fluorescence L transmitted through the inner surface of face plate 2 is again reflected on the outer surface of face plate 2. Thus, a considerable portion of the fluorescence generated within the phosphor 1 is removed by reflections in the course of passage to the outside, and a good optical contact has not been obtained between the patternwise powdery coating layer as phosphor layer and the substrate as face plate 2.